Process of decomposing waterinsoluble phosphates



Patented Aug. 12, 1941 PROCESS OF DECOMPOSING WATER- INSOLUBLE PHOSPHATES Otto Balz, Ludwigshafen-on-the-Rhine,

and

Heinrich Hamacher, Frankenthal, Germany, assignors, by mesne assignments, to Walter H. Duisberg, New York, N. Y.

No Drawing. Application April 4, 1939, Serial No.

1 Claim.

The present invention relates to a process of decomposing water-insoluble phosphates.

In our copending application Ser. No. 213,186 we have disclosed (with a co-inventor) a process according to which crude phosphates can be rapidly decomposed by means of nitric acid even at a ordinary temperature and even in the cold, which is attended with considerable advantage. At the low temperatures and the concentrations used the separation of calcium nitrate takes place during the reaction or immediately thereafter. In this process a temperature not exceeding 25 C. is maintained during the decomposition and the decomposition is efiected with nitric acid of from 55-65 per cent, the temperatures and concentrations being so correlated as to obtain substantial crystallization of the calcium nitrate not later than the completion of the decomposition and at the reaction temperature.

We have now found that in the said process the calcium nitrate is separated in a specially well crystallised form by adding to the nitric acid, to the crude phosphate or to the mixture of both in which decomposition takes place, an amount of ammonium nitrate and/or potassium nitrate suflicient for the formation of the known calcium-ammonium nitrate or calcium-potassium nitrate double salts. It is especially suitable to maintain a temperature of from about to 25 C. during the decomposition.

The following example will further illustrate how the said invention may be carried out in practice, but the invention is not restricted to this example. The parts are by weight.

Example 1000 parts of Morocco phosphate are intro- In Germany April 7, 1938 duced at a temperature of 21 G. into 2000 parts of 65 per cent nitric acid in which 150 parts of ammonium nitrate are dissolved. While the crude phosphate is still being introduced, there begins the separation of the calcium-ammonium nitrate double salt which is completed a short time after all phosphate has been introduced In this way 1300 parts of well crystallised, readily filterable double salt having a content of 1..- per cent of ammonia-nitrogen are obtained.

What we claim is:

In the process of decomposing water-insoluble phosphates with nitric acid in an amount at least sufiicient to convert all the phosphates into calcium nitrate and phosphoric acid, in which process a temperature not exceeding 25 C. is maintained during the decomposition and the decomposition is effected with nitric acid of from to the temperatures and concentrations being so correlated as to obtain substantial crystallization of the calcium nitrate not later than the completion of the decomposition and at the reaction temperature, and the crystallized calcium nitrate is separated from the phosphoric acid containing reaction liquid, the improvement which comprises adding at any stage of the reaction at least one of the compounds ammonium nitrate and potassium nitrate in an amount sufficient for the formation of at least one of the known double salts calcium-ammonium nitrate and calcium-potassium nitrate, the crystallization of the calcium nitrate thus taking place in the form of at least one of the said double salts.

OTTO BALZ. HEINRICH HAMACHER. 

